Mineral oil additive



Patented Apr. 28, 1953 UNITED STATES PATENT FFICE MINERAL OIL ADDITIVEDelaware No Drawing. Application June 7, 1951,

Serial No. 230,418

Claims.

This invention relates to mineral oil compositions and particularly tolubricants containing a detergent additive.

The art of metallic detergents for lubricating oil compositions adaptedfor use in internal combustion engines is well known to have resulted insubstantial improvements in lubricants. These detergents areparticularly useful in lubricating oil compositions which are employedin internal combustion engines used in the operations of automobiles,aircraft and similar vehicles, including diesel engines, and improvetheir operation by preventing or retarding corrosion, piston ringsticking, cylinder wear, and carbon and varnish formation. However, whenmetallic detergents are used in lubricating compositions where oilconsumption is high and engine conditions are severe, such as inaircraft engines, or where such concentrations of metallic detergentsare used to maintain engine cleanliness under conditions where highdeposit fuels of cracked or high sulfur nature are used, such as inautomobile and diesel operation, the ash content from the metallicdetergent accumulates in the combustion chamber and causes pre-ignition,detonation, spark plug fouling, valve burning, and ultimate destructionof the engine.

It has been found that a good detergent and anti-oxidant can be preparedby first reacting a hydrocarbon with a sulfide of phosphorus, whichforms an acidic product, and then further reacting this product with anitrogen base. This product is particularly useful in reducing varnishformation and ring sticking in the operation of internal combustionengines, and has the further advantage that it does not leave a metallicdeposit or ash. However, this additive, when used alone, is noteffective in reducing the tendency of the lubricating oil to causecorrosion of the bronze valve guide of an automotive engine, and in factthis bronze corrosion is actually increased by the presence of theadditive.

It has been found, in accordance with the present invention, that if theadditive described above is employed in combination with a zincdithiocarbamate having organic groups which provide oil solubility, thebronze corrosion is markedly reduced. This efi-ect is synergistic andresults from a cooperative action of the two ingredients, the nature ofwhich is not known, since the zinc dithiocarbamate alone increases thebronze corrosion. The synergistic effect between the two ingredients ofthe additive also results in reducing the tendency of a lubricating oilto form coke at very high temperatures. This is a factor of importancein the operation of aviation engines.

The portion of the additive of the present invention which is formed byreacting a sulfide of phosphorus with a hydrocarbon and further reactingthe product with a nitrogen base may be referred to in thisspecification as Ingredient A. In forming this ingredient the sulfide ofphosphorus is reacted with an aliphatic hydrocarbon at a temperature ofabout 200 to about 600- F., and preferably from about 300 to 550 F.,using from about 1 to about 10, preferably about 2 to about 5, molecularproportions of hydrocarbon to one molecular proportion of the sulfide ofphosphorus in the reaction. It is advantageous to maintain anon-oxidizing atmosphere such as an atmosphere of nitrogen above thereaction mixture. Usually it is desirable to use an amount of thephosphorus sulfide that will completely react with the hydrocarbon sothat no further purification becomes necessary. In the case ofmonoolefin polymers the preferred ratio is one molecular proportion ofthe phosphorus sulfide to 2 to 5 molecular proportions of polymer. Insuch a case the reaction is continued until all or substantially all ofthe phosphorus sulfide has reacted. The reaction time is not critical,and the time required to cause the maximum amount of phosphorus sulfideto react will vary greatly with the temperature. A reaction time of 2 to10 hours is frequently necessary. If desired, the reaction product maybe further treated by blowing with steam, alcohol, ammonia, or an amineat an elevated temperature, say about 200 to 600 F., to improve theodor.

The sulfide of phosphorus which is employed in the reaction describedabove may be P2S3, P285, P 33, P4S7 or other phosphorus sulfide ormixtures of sulfides, and is preferably phosphorus pentasul-fide (PzSs)on account of its availability.

The hydrocarbon materials which may be reacted with the phosphorussulfide may be paraffins olefins, or olefin polymers, diolefins,acetylenes, petroleum fractions, such as lubricating oil fractions,brig-ht stock residuums, petrolatums, waxes, cracked cycle stocks, orcondensation products of petroleum fractions, solvent extracts ofpetroleum fractions, also aromatic hydrocarbons, such as benzene,alkylated benzenes, aromatic hydrocarbons derived from or contained inpetroleum oils, and the like.

,As examples ,of monoolefins maybe mentioned isobutylene, decene,.dodecene, centene (C16), octadecene (Cm), carotene (C26), melene (C30),olefinic extracts from gasoline or gasoline itself, cracked cycle stocksand polymers thereof, resin oils from crude oil, hydrocarbon coalresins, cracked waxes, dehydrohalogenated chlorinated waxes, and anymixed high molecular weight alkenes obtained by cracking petroleum oils.A preferred class of olefins are those having at least 20 carbon atomsper molecule, of which from about 12 to about 18 carbon atoms, andpreferably at least 15 carbon atoms, are in a long chain. Such olefinsmay be obtained by the dehydrogenation of paraffin waxes, by thedehydrohalogenation of long chain alkyl halides, by the synthesis ofhydrocarbons from C and H2, by the dehydration of alcohols, etc.

Another class of suitable olefinic materials are the monoolefinpolymers, in which the molecular weight ranges from 100 to 50,000,preferably from about 250 to about 10,000. These polymers may beobtained by the polymerization of low molecular weight monoolefinichydrocarbons, such as ethylene, propylene, butylene, isobutylene, normaland isoamylenes, or hexenes, or by the copolymerization of anycombination of the above monoolefinic materials.

Diolefins which may be employed include well known materials such asbutadiene, isoprene, chloroprene, cyclopentadiene,2,3-di-methylbutadiene, pentadiene-1,3, hexadiene-2A, and the like.Acetylene and substituted acetylenes may similarly be employed.

Another class of unsaturated hydrocarbon materials which may beadvantageously employed in the preparation of the additives of thisinvention are high molecular weight copolymers of low molecular weightmonoolefins and diolefins. The copolymer is prepared by controlledcopolymerization of a low molecular weight olefin and a non-aromatichydrocarbon showing the general formula CnHiZn-rr, in which a: is 2 or amultiple of 2, in the presence of a catalyst of the Friedel- Crafts orperoxide type. The low molecular weight olefin is preferably anisoolefin or a tertiary base olefin, preferably one having less than .7carbon atoms per molecule. Examples of such olefins are isobutylene,2-methylbutene-1, 2-ethylbutene-l, secondary and tertiary base amylenes,hexylenes, and the like. Examples of the non-aromatic hydrocarbons ofthe above formula which can be used are the conjugated diolefins listedin the preceding paragraph, diolefins such as 1,4-hexadiene, in whichthe double bond is not conjugated, as well as the acetylenes. Thecopolymerization is preferably carried out in the presence of aluminumchloride, boron fluoride, or benzoyl peroxide, and the oopolymer ispreferably one having a molecular Weight of about 1,000 to 30,000.

Another type of hydrocarbon material which may be similarly employed isa resin-like oil which has a molecular weight of from about 1,000 to2,000 or higher, obtained preferably from a paraffinic oil which hasbeen dewaxed and which is then treated with a liquified normally gaseoushydrocarbon, e. g., propane, to precipitate a heavy propane-insolublefraction. The latter is a substantially wax-free and asphaltfree producthaving a Saybolt viscosity at 210 F. of about 1,000 to about 4,000seconds or more.

Since the additives of the present invention are to be dissolved inmineral oils, the hydrocarbons which are reacted with a sulfide ofphosphorus will be chosen with a view to provide a product which issoluble in the oil base or which has such marginal solubility that itcan be plas-' ticized with a high molecular .weight alcohol, ester, orother plasticizer.

The reaction product of the sulfide of phosphorus and hydrocarbonpossess titratable acidity, and this acidity may be reduced orcompletely neutralized by reacting the product with a metallic ornon-metallic base. For the purposes of the present invention thenon-metallic bases, specifically the nitrogen bases, are preferred,since the additives formed from them do not leave an inorganic residue.The bases which may be employed include ammonia and any of the organicnitrogen bases, such as amines and amine derivatives, guanidines andtheir derivatives, morpholine, pyridine, quinoline, and like substances.

A highly preferred group of basic substances which may be employed inneutralizing the phosphorus sulfide-hydrocarbon product comprisesguanidine and its derivatives. The free base guanidine and itsderivatives may be used as well as basic acting salts of such bases, bywhich is meant salts of acids whose strength, measured on a pH scale, isless than that of the acidic phosphorus sulfide-hydrocarbon product.Such basic acting salts are, for example, the carbonates of guanidineand its derivatives. Alternatively, the final products may be formed bydouble decomposition of a salt of guanidine or guanidine derivative, e.g., guanidine hydrochloride or sulfate, with a metal salt of thephosphorus sulfide-hydrocarbon reaction product. Although guanidine andits salts are preferred, substituted guanidines may be used. Broadly,the guanidine type basic compounds which may be reacted in accordancewith the present invention, may be defined by the formula in which R1,R2, and R3 represent hydrogen or hydrocarbon groups containing 1 to 20carbon atoms, e. g., straight chain alkyl groups, such as methyl, ethyl,propyl, butyl, also higher straight and branched chain alkyl groups,such as octyl, isooctyl, Z-ethylhexyl, decyl, dodecyl, tetradecyl, cetyland stearyl radicals. R1, R2 and R3 may also represent cycloalkyl,arylalkyl, aryl or alkylaryl groups, for example, methylcyclohexyl,phenylethyl, phenyl, cresyl, and tert.-butylphenyl groups. It will beunderstood that R1, R2 and R: can be the same or different atoms orgroups in the same molecule. However, in the case of a substitutedguanidine it is most preferable to employ symmetrically tri-substitutedcompounds, and alkyl and cycloalkyl groups are the more preferred typesof substituting groups. These include the symmetrical trialkyl,trinaphthenyl, and triarylalkyl guanidines. Also highly preferredclasses of substituted guanidines include the monoalkyl, mononaphthenyl,and monoaralkyl guanidines; unsymmetrical dialkyl, dinaphthenyl anddiarylalkyl guanidines. Somewhat less preferable but still usefulclasses are the symmetrical dialkyl. dinaphthenyl, and diaryl alkylguanidines and the mono-, di-, and triaryl guanidines. Still othersubstituted guanidines maybe used, such as biguanide, dicyandiamide, anddicyandiamidine.

Specific examples of basic acting compounds illustrating theabove-described types are the following:

Guanidine a-Methylguanidine a-Ethylguanidine a-Hexylguanidinesymmetrical Trimethylguanidine Triethylguanidine TrioctadecylguanidineTricyclohexylguanidine Tribenzylguanidine Triphenylguanidine Carbonatesof any of the abovedisted compounds.

The neutralizing reaction, in which the nitrogen base is reacted withthe phosphorus sulfidehydrocarbon product, may be carried out,preferably in a non-oxidizing atmosphere, by contacting the phosphorussulfide-hydrocarbon reaction product either as such or dissolved in asuitable solvent such as naphtha, with a basic compound. preferably at atemperature of about 100 to 400 F. It is desirable to employ at leastenough of the basic compound to neutralize the titratable acidity of thephosphorus sulfide-hydrocarbon product. In practice a somewhat greateramount of basic compound is generally employed, sincethis can be reactedin proportions greater than that required for neutralization. When thebasic compound is added in the form of a carbonate, the completion ofthe reaction is indicated by a cessation of carbon dioxide evolution. Ithas been found that somewhat superior products are formed when a watersoluble basic compound, e. g., guanidine carbonate, is dissolved in'ormixed with water when contacted with the phosphorus sulfide-hydrocarbonreaction product. In the case of guanidine carbonate it is preferable toemploy a mixture of the salt and water containing 30 to 70% by weight ofthe salt.

The second ingredient of the compounded additive of the presentinvention may be referred to as Ingredient B and is a zinc salt of adithiocarbamatic acid having organic groups of sufficient chain lengthto provide oil solubility. More specifically, this ingredient may bedefinedas a compound of the formula 6 wherein R, and R may eachrepresent hydrogen or a hydrocarbon radical, at least one of them beinga radical. The hydrocarbon radicals may be aliphatic, cyclo'aliphatic oraromatic, but at least one aliphatic or cycloaliphatic hydrocarbonradical must be attached to each nitrogen atom, and there should be atotal of at least six carbon atoms in the two groups attached to thenitrogen. The more preferred compounds are thezinc dialkyl ordicycloalkyl dithiocarbamates. The following are typical compoundssuitable for use as Ingredient B:

Zinc di-n-butyldithiocarbamate Zinc diisobutyldithiocarbainate Zincdi-n-amyldithiocarbarnate Zinc di-n-octyldithiocarbamate Zincdi-tert.-octyldithioc'arbamate Zinc mono-n-hexyldithiocarbam'ate Zincn-butylphenyldithiocarbamate Zinc dicyclohexyldithiocarbamate Zincdi-n-butenyldithiocarbamate Zinc di-wax-alkyldithiocarbamate The amountof Ingredient A in the combined additive of the present invention isequal to and preferably somewhat greater than that of Ingredient B on aweight basis; and in general the proportion of Ingredient A is from 1 to20 parts by weight to one part by weight of Ingredient B. When thecombined additive is employed in a mineral lubricating oil, it ispreferably added in concentrations of about 0.1 to about 20% by weightand more generally concentrations of 1.0 to 6.0% are employed. Theproportions giving the best results will vary somewhat according to thenature of the ingredients of the additive and the specific purpose whichthe lubricant is to serve in a given case. For commercial purposes, itis convenient to prepare concentrated oil solutions in which the amountof the combined additive in the composition ranges from 20 to 50% byweight, and to transport and store them in such form. In preparing alubricating oil composition for use as a crankcase lubricant, theadditive concentrate is merely blended in the base oil in the requiredamount.

Below are given a description of the preparation of an additive of thetype described above as well as laboratory and engine tests of theproperties of lubricating oils containing the same. It is to beunderstood that these examples are given as illustrations of the presentinvention and are not to be construed as limiting the scope thereof inany way,

EXAMPLE 1 Preparation of PzSs-bright stock-guanidine 665 gals. of phenolextracted Mid-Continent bright stock was charged to a reactor and heatedto 250 F., nitrogen being blown through the charge and vigorousmechanical agitation maintained during the entire heating period. 25 cc.of a silicone polymer was added to prevent foaming. 485 lbs. of P2S5 wasadded over a fifteen minute period and the entire mixture was heated to430-460" F. for about two hours, soaked at about F. for three hours, andthen filtered through Hi-flow (a filter aid). 3,865 lbs. of this productwas charged to a reactor and heated to F.. nitrogen blowing andmechanical agitation being maintained during the entire heating period.A solution of 387 lbs. of guanidine carbonate and 752 lbs. of waterwasprepared by heating the two components to ISO-250 ,F. This solutionwas EXAMPLE 2 Bronze corrosion test A laboratory bronze corrosion testwas applied to oil blends containing the product of Example 1, with andwithout the further addition of zinc dibutyldithiocarbamate. The testwas carried out by heating the oil sample to 650 F. in the presence of aquarter-section of a bronze aviation engine valve guide for a period of17 hours, and the loss in weight of the valve guide section, afterwashing in cyanide solution, determined. Blends were made in threedifferent aviation lubricating oils prepared from base stocks derivedfrom different types of crude oils. The results obtained were asfollows:

Oil l+3% product of Example l+0.5%

dithiocarbamatc 0. 88

Oil II l n 0. 46 Oil II+C product of Example 1 0. 79 Oil Il+3% productof Example l+0.5% zinc dibutyl- 2 dithiocarbamatc 0. 55

perature at BOO-520 F. At the end of the test the oil is poured from thecup which is then washed with naphtha and dried with air to a constantweight. The difference in the weight of the cup before and after thetest is taken as the amount of coke deposit. In the data given below thedesignations Oil I and Oil II refer to the base oils described inExample 2. The results are as follows:

EXAMPLE 4 Aviation C. F. R. engine test Some of the oil blends of thetype described in the preceding examples were evaluated in a C. F. R.engine test, which was conducted for a period of 100 hours, the C. F. R.engine being operated at 1800 R. P. M. and 4 brake horsepower. The oilswere rated by a clemerit system, wherein a perfectly clean surface isgiven a rating of zero while a rating of 10 is given to the worsecondition which could be expected on that surface. Oils I, II and IIIare the same as in Example 2. The results are shown in the followintable:

EXAMPLE 3 Coking test The products of the present invention may beemployed not only in ordinary hydrocarbon lubricating oils but also inthe heavy duty type of lubricating oils which have been compounded withsuch detergent type additives as metal soaps, metal petroleumsulfonates, metal phenates, metal alcoholates, metal alkyl phenolsulfides, metal organo phosphates, phosphites, thiophosphates, andthiophosphites, metal xanthates and thio-xanthates, metalthiocarbamates, and the like. Other types of additives, such as phenolsand phenol sulfides, may also be present.

The lubricating oil base stock used in the compositions of thisinvention may be straight mintemperature is kept at 550 F. and thejackettemeral lubricating oils or distillates derived from parafiinic,naphthenic, asphaltic or mixed base crudes, or if desired, variousblended oils may be employed as well as residuals, particularly thosefrom which asphaltic constituents have been carefully removed. The oilsmay be refined by conventional methods using acid, alkali and/or clay orother agents such as aluminum chloride, or they may be extracted oilsproduced by solvent extraction with solvents such as phenol, sulfurdioxide, etc. Hydrogenated oils or white oils may be employed as well assynthetic oils resembling petroleum oils, prepared, for example, by thepolymerization of olefins or by the reaction of oxides of carbon withhydrogen or by the hydrogenation of coal or its products.

For the best results the base stock chosen should normally be an oilwhich with the new additive present gives the optimum performance in theservice contemplated. However, since one advantage of the additives isthat their use also makes feasible the employment of less satisfactorymineral oils, no strict rule can be laid down for the choice of the basestock. The additives are normally suificiently soluble in the basestock, but in some cases auxiliary solvent agents may be used. Thelubricating oils will usually range from about to to 150 seconds(Saybolt) viscosity of 210 F. The viscosity index may range from to 100or even higher.

Other agents than those which have been mentioned may be present in theoil composition, such as dyes, pour point depressants, heat thickenedfatty oils, sulfurized fatty oils, sludge dispersers, antioxidants,thickners, viscosity index improvers, oiliness agents, resins, rubber,olefin polymers, and the like.

Assisting agents which are particularly desirable as plasticizers anddefoamers are the higher alcohols having preferably 8-20 carbon atoms,e. g. octyl alcohol, lauryl alcohol, stearyl alcohol, and the like.

In addition to being employed in lubricants, the additives of thepresent invention may alsobe used in other mineral oil products such asmotor fuels, heating oils, hydraulic fluids, torque converter fluids,cutting oils, flushing oils, turbine oils, transformer oils, industrialoils, process oils, and the like, and generally as antioxidants inmineral oil products. They may also be used in gear lubricants, greasesand other products containin mineral oils as ingredients.

What is claimed is:

1. A mineral oil containing about 0.1 to about 20% by weight of anadditive consisting of (A) a product obtained by reacting a phosphorussulfide with a hydrocarbon and neutralizing the acidic reaction productthus formed with a nitrogen base, and (B) a zinc dithiocarbamate of theformula SC IN in which R and R are members of the group consisting ofhydrogen and hydrocarbon radicals,

at least one being a member of the group consisting of aliphatic andcycloaliphatic hydrocarbon radicals, the total number of carbon atoms inthe two groups being at least 6, the ratios of the two ingredients ofthe additive being from 5 to 20 parts by weight of A to one part byweight of B.

2. A composition according to claim 1 in which the mineral oil is alubricating oil fraction.

3. A composition according to claim 1 in which the nitrogen base is anorganic base reacting compound selected from the group consisting of:(1) free bases of the composition in which R1, R2 and R3 are eachmembers of the group consisting of hydrogen and hydrocarbon radicalscontaining 1 to 20 carbon atoms, and (2) basic reacting salts of theaforementioned free bases.

4. A composition according to claim 1 in which the zinc dithiocarbamateis a zinc dialkyldithiocarbamate having a total of at least 6 carbonatoms in the two alkyl groups.

5. A composition according to claim 3 in which the zinc dithiocarbamateis a zinc dialkyldithiocarbamate having a total of at least 6 carbonatoms in the two alkyl groups.

6. A composition according to claim 1 in which the basic reactingcompound is guanidine carbonate.

'7. A mineral lubricating oil containing about 0.1 to about 20% byweight of an additive consisting of (A) the product obtained by reactingphosphorus pentasulfide with a lubricating oil bright stock andneutralizing the product thus formed with guanidine carbonate, and (B)zinc dibutyldithiocarbamate, the ratios of the two in gredients of theadditive being from 5 to 20 parts by weight of A to one part by weightof B.

8. A mineral lubricating oil containing about 3% by weight of theproduct obtained by reactillg phosphorus pentasulfide with a lubricatingoil bright stock and neutralizing the product thus formed with guanidinecarbonate, and about 0.5% by weight of zinc dibutyldithiocarbamate.

9. A composition consisting essentially of a mineral lubricating oil andan additive as defined in claim 1, the amount of said additive in thecomposition being 20-50% by weight.

10. A composition consisting essentially of a mineral lubricating oiland an additive as defined in claim 7, the amount of said product in thecomposition being 20-50% by weight.

ROBERT H. JONES. LEONARD E. MOODY.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,316,090 Kelso Apr. 6, 1943 2,409,686 McNab Oct. 22, 19462,412,903 Miller et al Dec. 17, 1946 2,422,075 Bray June 10, 19472,451,3 l5 McNab et a1 Oct. 12, 1948

1. A MINERAL OIL CONTAINING ABOUT 0.1 TO ABOUT 20% BY WEIGHT OF ANADDITIVE CONSISTING OF (A) A PRODUCT OBTAINED BY REACTING A PHOSPHORUSSULFIDE WITH A HYDROCARBON AND NEUTRALIZING THE ACIDIC REACTION PRODUCTTHUS FORMED WITH A NITROGEN BASE, AND (B) A ZINC DITHIOCARBAMATE OF THEFORMULA